Mono: C# compiler bug with property inheritance

The bug appeared quite unexpectedly.
In Visual Studio code sample below compiled fine. But doing the same with Mono C# compiler results in error: Compiler Error CS0546: 'Derived2.Accessor.set': cannot override because 'Base.Accessor' does not have an overridable set accessor.
It must've been a bug with the compiler I thought to myself. Mono bugzilla search confirmed that bug was there.

Here is the code sample that produces error report (workaround is described under it):

abstract class Base
    {
        public virtual string Accessor
        {
            get { return "base"; }
            set { }
        }
    }

    class Derived1 : Base
    {
        public override string Accessor
        {
            get { return base.Accessor; }
        }
    }

    class Derived2 : Derived1
    {
        public override string Accessor
        {
            set { }
        }
    }

Workaround for this error is to add set property to Derived1 class:

public override string Accessor
        {
            get { return base.Accessor; }
            set { base.Accessor = value; }
        }

Happy coding :)